/*
 * ASN.1 buffer writing functionality
 *
 *  Copyright The Mbed TLS Contributors
 *  SPDX-License-Identifier: Apache-2.0 OR GPL-2.0-or-later
 *
 *  This file is provided under the Apache License 2.0, or the
 *  GNU General Public License v2.0 or later.
 *
 *  **********
 *  Apache License 2.0:
 *
 *  Licensed under the Apache License, Version 2.0 (the "License"); you may
 *  not use this file except in compliance with the License.
 *  You may obtain a copy of the License at
 *
 *  http://www.apache.org/licenses/LICENSE-2.0
 *
 *  Unless required by applicable law or agreed to in writing, software
 *  distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
 *  WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 *  See the License for the specific language governing permissions and
 *  limitations under the License.
 *
 *  **********
 *
 *  **********
 *  GNU General Public License v2.0 or later:
 *
 *  This program is free software; you can redistribute it and/or modify
 *  it under the terms of the GNU General Public License as published by
 *  the Free Software Foundation; either version 2 of the License, or
 *  (at your option) any later version.
 *
 *  This program is distributed in the hope that it will be useful,
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *  GNU General Public License for more details.
 *
 *  You should have received a copy of the GNU General Public License along
 *  with this program; if not, write to the Free Software Foundation, Inc.,
 *  51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 *  **********
 */

#if !defined(MBEDTLS_CONFIG_FILE)
#include "nettls/config.h"
#else
#include MBEDTLS_CONFIG_FILE
#endif

#if defined(MBEDTLS_ASN1_WRITE_C)

#include "nettls/asn1write.h"

#include <string.h>

#if defined(MBEDTLS_PLATFORM_C)
#include "nettls/platform.h"
#else
#include <stdlib.h>
#define mbedtls_calloc calloc
#define mbedtls_free   free
#endif

int mbedtls_asn1_write_len(unsigned char** p, unsigned char* start, size_t len)
{
    if (len < 0x80) {
        if (*p - start < 1)
            return (MBEDTLS_ERR_ASN1_BUF_TOO_SMALL);

        *--(*p) = (unsigned char)len;
        return (1);
    }

    if (len <= 0xFF) {
        if (*p - start < 2)
            return (MBEDTLS_ERR_ASN1_BUF_TOO_SMALL);

        *--(*p) = (unsigned char)len;
        *--(*p) = 0x81;
        return (2);
    }

    if (len <= 0xFFFF) {
        if (*p - start < 3)
            return (MBEDTLS_ERR_ASN1_BUF_TOO_SMALL);

        *--(*p) = (len)&0xFF;
        *--(*p) = (len >> 8) & 0xFF;
        *--(*p) = 0x82;
        return (3);
    }

    if (len <= 0xFFFFFF) {
        if (*p - start < 4)
            return (MBEDTLS_ERR_ASN1_BUF_TOO_SMALL);

        *--(*p) = (len)&0xFF;
        *--(*p) = (len >> 8) & 0xFF;
        *--(*p) = (len >> 16) & 0xFF;
        *--(*p) = 0x83;
        return (4);
    }

#if SIZE_MAX > 0xFFFFFFFF
    if (len <= 0xFFFFFFFF)
#endif
    {
        if (*p - start < 5)
            return (MBEDTLS_ERR_ASN1_BUF_TOO_SMALL);

        *--(*p) = (len)&0xFF;
        *--(*p) = (len >> 8) & 0xFF;
        *--(*p) = (len >> 16) & 0xFF;
        *--(*p) = (len >> 24) & 0xFF;
        *--(*p) = 0x84;
        return (5);
    }

#if SIZE_MAX > 0xFFFFFFFF
    return (MBEDTLS_ERR_ASN1_INVALID_LENGTH);
#endif
}

int mbedtls_asn1_write_tag(unsigned char** p, unsigned char* start, unsigned char tag)
{
    if (*p - start < 1)
        return (MBEDTLS_ERR_ASN1_BUF_TOO_SMALL);

    *--(*p) = tag;

    return (1);
}

int mbedtls_asn1_write_raw_buffer(unsigned char** p, unsigned char* start, const unsigned char* buf, size_t size)
{
    size_t len = 0;

    if (*p < start || (size_t)(*p - start) < size)
        return (MBEDTLS_ERR_ASN1_BUF_TOO_SMALL);

    len = size;
    (*p) -= len;
    memcpy(*p, buf, len);

    return ((int)len);
}

#if defined(MBEDTLS_BIGNUM_C)
int mbedtls_asn1_write_mpi(unsigned char** p, unsigned char* start, const mbedtls_mpi* X)
{
    int ret;
    size_t len = 0;

    // Write the MPI
    //
    len = mbedtls_mpi_size(X);

    if (*p < start || (size_t)(*p - start) < len)
        return (MBEDTLS_ERR_ASN1_BUF_TOO_SMALL);

    (*p) -= len;
    MBEDTLS_MPI_CHK(mbedtls_mpi_write_binary(X, *p, len));

    // DER format assumes 2s complement for numbers, so the leftmost bit
    // should be 0 for positive numbers and 1 for negative numbers.
    //
    if (X->s == 1 && **p & 0x80) {
        if (*p - start < 1)
            return (MBEDTLS_ERR_ASN1_BUF_TOO_SMALL);

        *--(*p) = 0x00;
        len += 1;
    }

    MBEDTLS_ASN1_CHK_ADD(len, mbedtls_asn1_write_len(p, start, len));
    MBEDTLS_ASN1_CHK_ADD(len, mbedtls_asn1_write_tag(p, start, MBEDTLS_ASN1_INTEGER));

    ret = (int)len;

cleanup:
    return (ret);
}
#endif /* MBEDTLS_BIGNUM_C */

int mbedtls_asn1_write_null(unsigned char** p, unsigned char* start)
{
    int ret;
    size_t len = 0;

    // Write NULL
    //
    MBEDTLS_ASN1_CHK_ADD(len, mbedtls_asn1_write_len(p, start, 0));
    MBEDTLS_ASN1_CHK_ADD(len, mbedtls_asn1_write_tag(p, start, MBEDTLS_ASN1_NULL));

    return ((int)len);
}

int mbedtls_asn1_write_oid(unsigned char** p, unsigned char* start, const char* oid, size_t oid_len)
{
    int ret;
    size_t len = 0;

    MBEDTLS_ASN1_CHK_ADD(len, mbedtls_asn1_write_raw_buffer(p, start, (const unsigned char*)oid, oid_len));
    MBEDTLS_ASN1_CHK_ADD(len, mbedtls_asn1_write_len(p, start, len));
    MBEDTLS_ASN1_CHK_ADD(len, mbedtls_asn1_write_tag(p, start, MBEDTLS_ASN1_OID));

    return ((int)len);
}

int mbedtls_asn1_write_algorithm_identifier(unsigned char** p, unsigned char* start, const char* oid, size_t oid_len, size_t par_len)
{
    int ret;
    size_t len = 0;

    if (par_len == 0)
        MBEDTLS_ASN1_CHK_ADD(len, mbedtls_asn1_write_null(p, start));
    else
        len += par_len;

    MBEDTLS_ASN1_CHK_ADD(len, mbedtls_asn1_write_oid(p, start, oid, oid_len));

    MBEDTLS_ASN1_CHK_ADD(len, mbedtls_asn1_write_len(p, start, len));
    MBEDTLS_ASN1_CHK_ADD(len, mbedtls_asn1_write_tag(p, start, MBEDTLS_ASN1_CONSTRUCTED | MBEDTLS_ASN1_SEQUENCE));

    return ((int)len);
}

int mbedtls_asn1_write_bool(unsigned char** p, unsigned char* start, int boolean)
{
    int ret;
    size_t len = 0;

    if (*p - start < 1)
        return (MBEDTLS_ERR_ASN1_BUF_TOO_SMALL);

    *--(*p) = (boolean) ? 255 : 0;
    len++;

    MBEDTLS_ASN1_CHK_ADD(len, mbedtls_asn1_write_len(p, start, len));
    MBEDTLS_ASN1_CHK_ADD(len, mbedtls_asn1_write_tag(p, start, MBEDTLS_ASN1_BOOLEAN));

    return ((int)len);
}

int mbedtls_asn1_write_int(unsigned char** p, unsigned char* start, int val)
{
    int ret;
    size_t len = 0;

    if (*p - start < 1)
        return (MBEDTLS_ERR_ASN1_BUF_TOO_SMALL);

    len += 1;
    *--(*p) = val;

    if (val > 0 && **p & 0x80) {
        if (*p - start < 1)
            return (MBEDTLS_ERR_ASN1_BUF_TOO_SMALL);

        *--(*p) = 0x00;
        len += 1;
    }

    MBEDTLS_ASN1_CHK_ADD(len, mbedtls_asn1_write_len(p, start, len));
    MBEDTLS_ASN1_CHK_ADD(len, mbedtls_asn1_write_tag(p, start, MBEDTLS_ASN1_INTEGER));

    return ((int)len);
}

int mbedtls_asn1_write_tagged_string(unsigned char** p, unsigned char* start, int tag, const char* text, size_t text_len)
{
    int ret;
    size_t len = 0;

    MBEDTLS_ASN1_CHK_ADD(len, mbedtls_asn1_write_raw_buffer(p, start, (const unsigned char*)text, text_len));

    MBEDTLS_ASN1_CHK_ADD(len, mbedtls_asn1_write_len(p, start, len));
    MBEDTLS_ASN1_CHK_ADD(len, mbedtls_asn1_write_tag(p, start, tag));

    return ((int)len);
}

int mbedtls_asn1_write_utf8_string(unsigned char** p, unsigned char* start, const char* text, size_t text_len)
{
    return (mbedtls_asn1_write_tagged_string(p, start, MBEDTLS_ASN1_UTF8_STRING, text, text_len));
}

int mbedtls_asn1_write_printable_string(unsigned char** p, unsigned char* start, const char* text, size_t text_len)
{
    return (mbedtls_asn1_write_tagged_string(p, start, MBEDTLS_ASN1_PRINTABLE_STRING, text, text_len));
}

int mbedtls_asn1_write_ia5_string(unsigned char** p, unsigned char* start, const char* text, size_t text_len)
{
    return (mbedtls_asn1_write_tagged_string(p, start, MBEDTLS_ASN1_IA5_STRING, text, text_len));
}

int mbedtls_asn1_write_bitstring(unsigned char** p, unsigned char* start, const unsigned char* buf, size_t bits)
{
    int ret;
    size_t len = 0;
    size_t unused_bits, byte_len;

    byte_len = (bits + 7) / 8;
    unused_bits = (byte_len * 8) - bits;

    if (*p < start || (size_t)(*p - start) < byte_len + 1)
        return (MBEDTLS_ERR_ASN1_BUF_TOO_SMALL);

    len = byte_len + 1;

    /* Write the bitstring. Ensure the unused bits are zeroed */
    if (byte_len > 0) {
        byte_len--;
        *--(*p) = buf[byte_len] & ~((0x1 << unused_bits) - 1);
        (*p) -= byte_len;
        memcpy(*p, buf, byte_len);
    }

    /* Write unused bits */
    *--(*p) = (unsigned char)unused_bits;

    MBEDTLS_ASN1_CHK_ADD(len, mbedtls_asn1_write_len(p, start, len));
    MBEDTLS_ASN1_CHK_ADD(len, mbedtls_asn1_write_tag(p, start, MBEDTLS_ASN1_BIT_STRING));

    return ((int)len);
}

int mbedtls_asn1_write_octet_string(unsigned char** p, unsigned char* start, const unsigned char* buf, size_t size)
{
    int ret;
    size_t len = 0;

    MBEDTLS_ASN1_CHK_ADD(len, mbedtls_asn1_write_raw_buffer(p, start, buf, size));

    MBEDTLS_ASN1_CHK_ADD(len, mbedtls_asn1_write_len(p, start, len));
    MBEDTLS_ASN1_CHK_ADD(len, mbedtls_asn1_write_tag(p, start, MBEDTLS_ASN1_OCTET_STRING));

    return ((int)len);
}

/* This is a copy of the ASN.1 parsing function mbedtls_asn1_find_named_data(),
 * which is replicated to avoid a dependency ASN1_WRITE_C on ASN1_PARSE_C. */
static mbedtls_asn1_named_data* asn1_find_named_data(mbedtls_asn1_named_data* list, const char* oid, size_t len)
{
    while (list != NULL) {
        if (list->oid.len == len && memcmp(list->oid.p, oid, len) == 0) {
            break;
        }

        list = list->next;
    }

    return (list);
}

mbedtls_asn1_named_data*
    mbedtls_asn1_store_named_data(mbedtls_asn1_named_data** head, const char* oid, size_t oid_len, const unsigned char* val, size_t val_len)
{
    mbedtls_asn1_named_data* cur;

    if ((cur = asn1_find_named_data(*head, oid, oid_len)) == NULL) {
        // Add new entry if not present yet based on OID
        //
        cur = (mbedtls_asn1_named_data*)mbedtls_calloc(1, sizeof(mbedtls_asn1_named_data));
        if (cur == NULL)
            return (NULL);

        cur->oid.len = oid_len;
        cur->oid.p = mbedtls_calloc(1, oid_len);
        if (cur->oid.p == NULL) {
            mbedtls_free(cur);
            return (NULL);
        }

        memcpy(cur->oid.p, oid, oid_len);

        cur->val.len = val_len;
        cur->val.p = mbedtls_calloc(1, val_len);
        if (cur->val.p == NULL) {
            mbedtls_free(cur->oid.p);
            mbedtls_free(cur);
            return (NULL);
        }

        cur->next = *head;
        *head = cur;
    } else if (cur->val.len < val_len) {
        /*
         * Enlarge existing value buffer if needed
         * Preserve old data until the allocation succeeded, to leave list in
         * a consistent state in case allocation fails.
         */
        void* p = mbedtls_calloc(1, val_len);
        if (p == NULL)
            return (NULL);

        mbedtls_free(cur->val.p);
        cur->val.p = p;
        cur->val.len = val_len;
    }

    if (val != NULL)
        memcpy(cur->val.p, val, val_len);

    return (cur);
}
#endif /* MBEDTLS_ASN1_WRITE_C */
